1. Field of the Invention
The present invention relates to a storage device and a control apparatus of the storage device that carry out, during a Viterbi decoding process, a correction of read signals that are read from a head when reading predetermined data that is stored in the storage medium.
2. Description of the Related Art
A storage device that stores data (for example, a magnetic disk device, a magneto optical disk device, an optical disk device etc.) commonly includes a structure that includes a function called a failure prediction function such that upon determining that the storage device is in a condition that is likely to cause occurrence of a failure (occurrence of a failure in a head or a circuit inside the storage device), the storage device itself issues a warning to a host device (see, for example, Japanese Patent Application Laid-open No. 2004-342168).
For example, as shown in FIG. 9, during execution of a read process of data by a magnetic disk device 1, read signals that are read by a head 14 are subjected to a Viterbi decoding process inside a read channel 6 and sent to a format control unit 5. Next, the format control unit 5 checks whether the received data includes an error, and attempts a correction if the data includes an error (error correcting code (ECC) process). If the ECC process cannot correct the error, the format control unit 5 attempts a retry as a read error. Based on a number of retries and a total number of sectors that are subjected to a retry process, the format control unit 5 calculates an error rate, and if the error rate exceeds a predetermined threshold, the format control unit 5 issues a report (see FIG. 10) to the host device that is connected via a host interface (IF) etc.
However, in the conventional technology, occurrence of the read error cannot be predicted beforehand and avoided. In other words, in the conventional technology, calculation of the error rate that leads to the storage device notifying the host device of the warning of occurrence of failure is based on occurrence of the read error. Because notification of the warning to the host device is carried out after the read error has occurred, occurrence of the read error cannot be predicted beforehand and avoided.